Generally, iron caterpillars have been commonly used as the wheels for the work vehicles under the bad working conditions, such as a steep and rough road condition. However, as the iron caterpillars involve a heavy weight, a poor fuel efficiency and a loud noise, elastic crawlers have been recently introduced instead of the iron caterpillars.
The elastic crawler has a crawler body, and cores. The crawler body is based on an elastic material with a shape of an endless track. The cores are embedded in the crawler body with right and left wings extended left and right from the center of the crawler body, that is, in the width direction of the crawler body. The cores are arranged in the longitudinal direction of the track parallel to each other with a predetermined distance.
Raised lugs are formed at the ground contact side of the crawler body, and concave earth removal portions are disposed between the lug neighbors. The lugs are divided into left and right to the center of the crawler body in the width direction thereof, and overlapped with left and right wings of the cores, respectively. Japanese Patent Laid-open Publication No. 2002-29461 discloses such an elastic crawler.
With the elastic crawler, the one-sided lugs have ground contact surfaces overlapped with the projections of the neighboring wings in the longitudinal track direction, and the opposite-sided lugs have ground contact surfaces overlapped with the projections of the corresponding wings.
The lengths of the ground contact surfaces of the left and the right lugs are different from each other, and those lengths with the respective left lugs as well as with the respective right lugs are also different from each other. The left and the right lugs differentiated in the ground contact length are arranged in a zigzag pattern.
With the elastic crawler disclosed at the above publication, the left and right lugs with ground contact surfaces differentiated in the ground contact length are arranged with a zigzag pattern, and overlapped with the projections of the wings, thereby enhancing the flexibility at a section for wrapping the crawler around the driving wheel, inhibiting the release of the crawler from the sprocket, and reducing the vibration.
However, in such an elastic crawler where the ground contact lengths of the ground contact surfaces of the left and right lugs are different from each other, the lug with a relatively short ground contact length is liable to be deteriorated in rigidity.
Furthermore, when the elastic crawler is circularly operated, the external forces applied to the left and the right lugs are differentiated, and this causes stress to the elastic crawler. In this case, cracks are liable to be made at the stress-concentrated area, resulting in deteriorated reliability and durability of the elastic crawler.
In addition, as the lugs having ground contact surfaces with different ground contact lengths are divided left and right from the center of the crawler body in the width direction thereof, and arranged in a zigzag pattern, any one of the pair of core neighbors is necessarily overlapped or straddled with the lug. For this reason, although slightly improved, it is not possible to obtain sufficient flexibility, and to completely remove the crawler release factor.